1. Field of the Invention
This invention relates to an adjustable press roller for adjusting and controlling the nip deflection between the roller and a counter roller, the roller having a hollow cylindrical shell which is arranged rotatably around a stationary yoke or support being provided with pressing means for regulating the nip pressure between the press roller and its counter roller. The pressing means are arranged for pressing against an inner wall of the shell, the pressing member and the inner wall of the shell having a sliding engagement therebetween. The pressing means are arranged in one or more rows in the longitudinal direction of the yoke or support.
The invention relates also to an arrangement for adjusting and controlling the nip deflection between a suction box and a counter roller. The invention provides a closed pressurization system which uses, in combination, a hydro-elastic pressure medium and piston arrangements for pressurizing the pressing means. The pressure medium preferably is a room temperature vulcanizing silicone elastomer compound which is cast in situ in a pressure medium space. The piston means are used for pressurizing the pressure medium which, in turn, pressurizes the pressing means for pressing the hollow cylinder toward the counter roller. The pressure medium can be pressurized preferably by means of thermal expansion, which is controlled, for example, by electrical heating means. Preferably, the pressure medium is pressurized by the combination of piston means and electrical heating means, wherein the piston means are used for initial pressurizing of the pressure medium and heating means are used for fine adjustment of the nip pressure. The piston means can be used by means of any mechanical or electrical known apparatus.
2. Prior Art
It is commonly known in the art that there are many hydraulically functioning pressure rollers, as the number of the prior art publications show. The use of prior art solutions, which employ hydrostatic support elements, is known from U.S. Pat. No. 4,328,744, British Pat. No. 641,466, German Pat No. 22 54 392 and U.S. Pat. Nos. 3,885,283, 4,520,723, 4,440,077, and 3,703,862. The prior art systems employ hydraulic support elements having a battery of cylinders and pistons to receive pressurized fluid to ensure accurate adjustment of pressure to the different kind of shoes pressurizing the roller sleeve. None of these prior art publications show any solutions wherein the thermal expansion of an elastomer is used as a pressurizing medium in a closed system for the pressing element.